for lime, i would start with 1 tablespoon,,,,its really strong if you dont have hard water.

my preferred suggestion is to add 10 gallons of regular pea gravel to each bed every couple weeks until it stabilizes, but no more 30 % of the media... be sure to get it down into the wet zone. you should see a change within a week.

To give any quantified advice, we need to know some pH history, pH of top-up water, and carbonate hardness of both system and top-up water. Many use oyster shells or grit in a mesh bag and place it in the water stream.

Jon, after we "talked" thru posts a while ago, I told you I'd keep tracking and see if my system did keep needing lime or potassium bicarbonate after it initially settled down... update is: nothing needed to raise ph of late at all. I just do my normal 2 teaspoons of phosphoric acid in each 5 gals of water I add from my tap (to counter act the 8.0-8.2 ph out of the tap) and the system has been staying right at 6.8-7.0.

BUT, I do only have (2) 10" -12" koi in my fish tank since the beginning...so am curious how ph will be effected in the spring with my first planned Tilapia stocking of about 35 fish.

Nice Bradly, good to know. I have also not yet needed to add anything other than hard too up water to maintain pH, though I suspect in the winter/spring that will change because my well water dilutes with rain, becoming 7.0 by March or so. Right now it is 8.8. If I go too long my large AP system falls to 6.0, but adding 8.8 top-up water brings it back to 7. I need to put an automatic filler, so that it will hopefully stay in the 6.4-6.6 range. That's my next project.

Yeah, I'm getting ready to run a water line over to near my sump tank with a hose bib so I can attach my chlorine filter right there and not need to have hose stretching across the yard. I too am going to come up with some sort of a automated fill system... but since my sump tank level rises and falls, it will more likely be like a timed flow along with meaured acid release with the water. Have to think this thru carefully though...or it could get crazy bad. :-)

I know that in cool weather my system uses about 20-25 gallons of water a week, and when it's 90-100s outside that number goes up to about 35 gallons a week.

I just finished my floating water heater and it's in my sump tank, it's a 1700w water heater stainless steel element-pretty tirkc if I do say so myself. Now concentrating on insulating my fish tank and sump both so that keeping water at maybe 50 for the koi all winter won't bankrupt me. In spring time Tilapia will take their place.

Jon Parr said:

Nice Bradly, good to know. I have also not yet needed to add anything other than hard too up water to maintain pH, though I suspect in the winter/spring that will change because my well water dilutes with rain, becoming 7.0 by March or so. Right now it is 8.8. If I go too long my large AP system falls to 6.0, but adding 8.8 top-up water brings it back to 7. I need to put an automatic filler, so that it will hopefully stay in the 6.4-6.6 range. That's my next project.